Ercolano Red is a natural earth containing clay tinted by iron oxide that gives an exceptionally warm red hue. Our Ercolano red, like French ocher, contains at least 20% iron oxide and is low in silica. Ercolano red is obtained from iron ore deposits near Ercolano, Italy.
Mars Red is the name given to the synthetic precipitated form of iron oxide.
Origin and History Ercolano Red is a red earth, which have been used as a pigment since prehistoric times and is perhaps the most widely used pigment for artists' paints.
Source Ercolano red is a red ocher obtained in the vicinity of Ercolano, named Herculaneum until 79 AD and Resina until 1969. Red ochers are natural earths containing clay tinted by iron oxide and is composed of hematite, and traces of gypsum (calcium sulfate) or calcite (calcium carbonate). Hematite is a mineral composed of iron oxide minerals (α-Fe2O3) that occur as natural earth. Depending upon the content of iron oxide and other minerals, the color of red ocher varies from deep red to brownish red. Red iron oxide minerals, such as hematite, are found around the world and have been used as pigments since prehistory.
Permanence and Compatibility Red ochers are among the most permanent colors among the artist's palette. It is compatible with all other pigments, and can be used with good results in all mediums.
Oil Absorption and Grinding Red ochers absorb a medium amount of oil, which may slow the drying of oil paint, but because iron oxide is a drier in oil, it dries fast and forms an excellent film.
Toxicity Red ochers are not considered toxic, but care should be used in handling the dry powder pigment to avoid inhaling the dust.